Cooling systems are widely used in the field of electric, electronic, low, medium and high voltage applications.
Power electronic devices must be cooled in operation, in order to avoid excessive temperatures and consequently failure of the devices. Typical applications feature not only high rates of heat generation by the devices, but also high power densities, for example, heat fluxes.
Water-cooled systems can generally deal well with high power density. However, such systems may be costly and may need an active, moving part in the form of a pump, which has a finite life and must be serviced. Also, water cooling systems are usually quite expensive.
Known air cooling systems, consisting of an array of fins extending from a base plate, may need no pump, but may need a fan in forced convection. However, as the heat transfer coefficient between fin surface and air is low, a large fin area is required for sufficient cooling performance. Further, if excessive air velocity, pressure drop, and noise level are to be avoided, a sufficient cross-section of the airflow must be provided. Such designs may result in bulky heat sinks with long, thick, and consequently heavy fins for acceptable fin efficiency. This drawback may be even made worse if one asks for a minimum spacing between adjacent fins in order to avoid clogging of the inter-fin channels in dirty air environment as may occur in major applications. A two phase cooler is described in EP 2 031 332 A1 showing a passive system based on the loop-thermosyphon principle.